The present invention relates to a method and apparatus for estimating, via radar, the trajectory of a projectile such as a rocket shell or a mortar shell. More particularly, the present invention relates to a radar system from which 3-dimensional coordinate information for the trajectory of an object is obtained by using two intersecting signal groups, each generated by a plurality of fan-shaped antenna lobes; and by applying an interferometric method to the signals.
It is well known that the location, as well as an estimate of origin, and an estimate of destination of an airframe like an aircraft can be detected using a conventional radar system. Similar information for a projectile such as a mortar shell can be obtained, using radar called mortar locating radar. With mortar locating radar, the firing point of the mortar shell can be estimated, even though the firing point is hidden behind the lay of the land, such as a hill or a mountain. The estimation can be made by: (1) covering two or three separate sectors with radar fan beams, each sector formed by successively scanning a pencil beam; (2) detecting the mortar shell as it successively passes through the sectors, by receiving reflected waves from the shell; (3) obtaining 3-dimensional coordinates of the shell, using the time information from the pencil beam scanning and the received reflected waves; (4) estimating the trajectory of the shell from the 3-dimensional coordinate information; and (5) estimating the firing point of the shell.
However, in conventional mortar locating radar, the pencil beam is used to cover the sectors of radar fan beams, so the number of the fan beams is limited to two or three. Consequently, if more fan beams are required, the radar system becomes very complicated. This is because a plurality of radar beams would have to be used, each having a different radio frequency (RF). Therefore, it is difficult to achieve high accuracy when estimating the trajectory and the firing position of a mortar shell using conventional motar locating radar.